Group III-V compounds, such as gallium arsenide (GaAs), and group IV materials, such as silicon germanium (SiGe) and germanium (Ge), have higher electron and hole mobility than that of silicon and an excellent carrier transport property, and are expected as next-generation semiconductor high-mobility channel materials.
A channel using a high-mobility material can be formed by polishing an object including a high-mobility material portion and a silicon material portion. In this case, when a polishing composition is used that can non-selectively polish and remove the high-mobility material portion and the silicon material portion, the high-mobility material portion and the silicon material portion can be simultaneously polished. The non-selective polishing of the high-mobility material portion and the silicon material portion enables a desired pattern shape to be formed in a suitable manner without producing a level difference between the high-mobility material portion and the silicon material portion. However, both a polishing composition conventionally used for polishing a group IV compound semiconductor substrate and described in, for example, Patent Document 1 or 2, and a polishing composition conventionally used for polishing a group III-V compound semiconductor substrate and described in, for example, Patent Document 3 or 4 are inferior in the capability of efficiently and non-selectively polishing and removing a high-mobility material portion and a silicon material portion. Those conventional polishing compositions are thus unsuitable for the purpose of simultaneously polishing a high-mobility material portion and a silicon material portion.